Am I the only one who has trouble tapping blind 1/4-20 holes? What a pain in
the ass!
I am doing better counting the thread rotations and reversing than setting
the depth stop.
Any tips from tap experts? I have a 500 or so holes to tap.
Machine is a Bridgeport mill with a Tap-Matic 50X
--
Stupendous Man,
Defender of Freedom, Advocate of Liberty

On 2009-12-02, Stupendous Man wrote:
Am I the only one who has trouble tapping blind 1/4-20 holes? What a pain in
the ass!
I am doing better counting the thread rotations and reversing than setting
the depth stop.
Any tips from tap experts? I have a 500 or so holes to tap.
Machine is a Bridgeport mill with a Tap-Matic 50X

Hmm ... how shallow are the blind holes?

Anyway -- what I do to set a Tap-Matic (of various sizes and
models) is to first measure how deep into the hole the tap will go, and
make a spacer bar to sit on the table as a reference for that depth.

Then, I pull down on the tap holder (with the tap mounted, to
disengage the dog clutch, rotate it a bit and release to let it sit on
top of the teeth of the dog clutch. This is as far down as the tap can
go under power.

Then I feed the spindle down and set the stop so it stops just
before the tip of the tap touches the reference spacer. (I usually do
this on a drill press, not a mill, but the mill probably has a more
precise depth stop.)

Then rotate the tap a little while still at the stop position,
to make sure that it retracts again. If it doesn't, or you can't rotate
it at all, then you probably actually have let the dog clutch re-engage,
so back out and try again. :-)

Now -- the one which I have which is in the size range of the
50X is a "Model A", which does not have the torque limit adjustment, but
which *does* have an adjustment for how far the dog clutch must travel
before it releases -- useful for self starting in shallow blind holes.

So -- first off -- how much chip clearance do you have (if you
are using spiral point (gun) taps?) There must be extra depth in blind
holes to collect the chips.

The spiral *flute* taps will pull the chips up instead of push
them forward, so they may offer better behavior in shallow blind holes.
I've not tried them, as most of my tapping is through holes, so get your
own experience with them and report it to the newsgroup.

And then there are thread forming taps, which produce no chips,
but which need greater torque to drive them. Whether the thread forming
taps will work for you is in part a function of what material you are
tapping.

The really nice thing for normal taps with the heads which have
the torque limit is you start with a new tap, adjust until it just
barely does not slip throughout the tapping cycle, and when it *does*
start slipping again, it is time to move to a new tap -- the one you
have is getting too dull to trust with power tapping.

I hope that this is some help,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Stupendous Man wrote:
Am I the only one who has trouble tapping blind 1/4-20 holes? What a
pain in the ass!
I am doing better counting the thread rotations and reversing than
setting the depth stop.
Any tips from tap experts? I have a 500 or so holes to tap.
Machine is a Bridgeport mill with a Tap-Matic 50X

Check your tap drills. Tolerances vary from brand to brand.
Had a good brand-name maker drill give me fits until I found the holes
it made were undersized. Destroyed a half dozen taps before I learned
that little lesson. Don't assume.


Good luck

Jim Vrzal
Holiday,Fl.

"Stupendous Man" wrote in message
...
Am I the only one who has trouble tapping blind 1/4-20 holes? What a pain
in the ass!
I am doing better counting the thread rotations and reversing than setting
the depth stop.
Any tips from tap experts? I have a 500 or so holes to tap.
Machine is a Bridgeport mill with a Tap-Matic 50X
--
Stupendous Man,
Defender of Freedom, Advocate of Liberty

We run the SPD series on our automatic units for customers all the time.
Never had a problem with depth control as they "fall" into reverse at some
point.

Maybe set it up so that the deepest the tap can possibly go is just short of
too deep but at 100% of the BP's stroke?

Heck... We've put an eight spindle head on a fixture driven by a TapMatic
and the customer has run probably close to a million tapped holes...
Something doesn't seem right - or the 50X is a different animal. Is it a
clutched head VS a self-reversing rigid drive head?

Regards,
Joe Agro, Jr.
(800) 871-5022
01.908.542.0244
Automatic / Pneumatic Drills: http://www.AutoDrill.com
Multiple Spindle Drills: http://www.Multi-Drill.com
Production Tapping: http://Production-Tapping-Equipment.com/
Flagship Site: http://www.Drill-N-Tap.com
VIDEOS: http://www.youtube.com/user/AutoDrill

V8013-R

"Stupendous Man" wrote in message
...
Am I the only one who has trouble tapping blind 1/4-20 holes? What a pain
in the ass!
I am doing better counting the thread rotations and reversing than setting
the depth stop.
Any tips from tap experts? I have a 500 or so holes to tap.
Machine is a Bridgeport mill with a Tap-Matic 50X
--
Stupendous Man,
Defender of Freedom, Advocate of Liberty

If you can count the rotations maybe that is the problem. Off the top of my
head I would run a 1/4" tap about 600-800 rpm in mild steel or 1200 rpm or
so in aluminum. What oil or lubricant are you using? What kind of tap? How
deep?

After I broke 3 taps this morning i used the old standby, the cordless
drill. Got them all done. perfect accurracy was not required.

The holes are only deep enough for 7 threads at 20 per inch, I am making car
door handles. The Tapmatic doesn't reach the part to start tapping when the
depth stop is set for neutral and retraction reverse as normal, so i was
counting the turns as it went in by a paint mark on the chuck at 300 RPM in
cast aluminum. Near as i can figure the clutch is erratic, as it workes fine
for 10 or so holes and then a tap snaps. I will take it apart when I have
time and make sure all the plates are clean and dry, this tapping head has
been around a while
--
Stupendous Man,
Defender of Freedom, Advocate of Liberty

On 2009-12-03, Stupendous Man wrote:
After I broke 3 taps this morning i used the old standby, the cordless
drill. Got them all done. perfect accurracy was not required.

The holes are only deep enough for 7 threads at 20 per inch, I am making car
door handles. The Tapmatic doesn't reach the part to start tapping when the
depth stop is set for neutral and retraction reverse as normal, so i was
counting the turns as it went in by a paint mark on the chuck at 300 RPM in
cast aluminum. Near as i can figure the clutch is erratic, as it workes fine
for 10 or so holes and then a tap snaps. I will take it apart when I have
time and make sure all the plates are clean and dry, this tapping head has
been around a while

It sounds as though you need the version which has an adjustment
for how much travel is needed to release the dog clutch to stop the
tapping and prepare for reverse. It is a knurled ring surrounding the
spindle, with a setscrew keeping it from turning until you back off the
setscrew. Only some versions of the tapping heads have this feature,
including my "Model A" (which does not have the adjustable clutch, and
perhaps not even a clutch at all.

Your counting the turns is dangerous, because you can't preduct
just where the thread will actually start, so you can wind up nearly a
full thread deeper.

With the adjustable dog clutch travel, you can set it so it will
start properly, and disengage at a precise depth, so you don't have to
worry -- just set the depth right and you are fine.

Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

It says right on the label, "Use the clutch only as a safety device, not
as stop in bottom holes."

"Stupendous Man" wrote in message
...
After I broke 3 taps this morning i used the old standby, the cordless
drill. Got them all done. perfect accurracy was not required.

The holes are only deep enough for 7 threads at 20 per inch, I am making
car door handles. The Tapmatic doesn't reach the part to start tapping
when the depth stop is set for neutral and retraction reverse as normal,
so i was counting the turns as it went in by a paint mark on the chuck at
300 RPM in cast aluminum. Near as i can figure the clutch is erratic, as
it workes fine for 10 or so holes and then a tap snaps. I will take it
apart when I have time and make sure all the plates are clean and dry,
this tapping head has been around a while
--
Stupendous Man,
Defender of Freedom, Advocate of Liberty

Stupendous Man wrote:
... was counting the turns as it went in by a paint mark on the chuck
at 300 RPM ...

I'm impressed - 300 RPM is 5 rev/sec. Being able to count paint marks
1/5 second apart is pretty good, I think. But I've never tried - is it
hard or not?

Bob

It says right on the label, "Use the clutch only as a safety device,
not as stop in bottom holes."

But when the hole is too short to use the tool normally, what can you do?
The clutch on the cordless drill worked just fine, didn't break a single
tap, although my wrists were a little sore the next day.

Counting the paint marks on the chuck was easy. Black or white marks were
hard to see, but a 1/2 inch wide red stripe showed up fine.

One of the drawbacks of operating a small, one-man shop is that the budget
is tight. Another is that I am over 100 miles from the nearest industrial
metal supplier, and 150 from any decent tool suppliers. I often machine at
slower than necessary speeds to conserve the tooling. I also save every tiny
piece of scrap as i may need it later. I have been know to make fixtures out
of Bondo and scrap lumber.
http://i221.photobucket.com/albums/d...e/IMG_2367.jpg
Part runs are usually pretty short. The boss will send me a design or part
to be modified, and first i have to figure out how to do it. Then, I figure
out how to do it with the materials present. Then, I figure out how to do it
with the existing tooling. Sometimes the part gets re-designed three times
before I make the first cut.

"Stupendous Man" wrote in message
...


It says right on the label, "Use the clutch only as a safety device,
not as stop in bottom holes."

But when the hole is too short to use the tool normally, what can you do?
The clutch on the cordless drill worked just fine, didn't break a single
tap, although my wrists were a little sore the next day.

Counting the paint marks on the chuck was easy. Black or white marks were
hard to see, but a 1/2 inch wide red stripe showed up fine.

One of the drawbacks of operating a small, one-man shop is that the budget
is tight. Another is that I am over 100 miles from the nearest industrial
metal supplier, and 150 from any decent tool suppliers. I often machine at
slower than necessary speeds to conserve the tooling. I also save every
tiny piece of scrap as i may need it later. I have been know to make
fixtures out of Bondo and scrap lumber.
http://i221.photobucket.com/albums/d...e/IMG_2367.jpg
Part runs are usually pretty short. The boss will send me a design or part
to be modified, and first i have to figure out how to do it. Then, I
figure out how to do it with the materials present. Then, I figure out how
to do it with the existing tooling. Sometimes the part gets re-designed
three times before I make the first cut.


I'm in the same boat.
Luckily, there are about 5 or 6 different Tap-Matics that came with the
business when we bought it... I wouldn't have been able to go out and buy
them new. I use the 50X almost every day... but the holes all go through.
I have two 50X's, a Model "A" that others have mentioned, a huge R7, and
a little "1A"... and they all work differently (designed for different
applications, I think). If I remember right, the R7 goes in and out at the
same speed... for old NC machines that had a set feed rate? The 50X has the
adjustable "safety" clutch and reverses at something like 1.5X the feed-in
speed, while the Model A and little 1A have the adjustable auto-feed depth
for blind holes.
I don't know if you could build a fixture for you part, where the part
would be clamped up under a spacer plate with a tapped hole in it... so that
you could get 3/8" or 1/2" of "feed" to start the Tap-Matic (tap through the
plate and into your part)? Then you could set the depth to 3/8" less than
the thickness of the plate + your hole depth, so the Tap-Matic would kick
out normally?